Interfacial α-FAPbI3 phase stabilization by reducing oxygen vacancies in SnO2−x

초록

Reducing nonradiative recombination in SnO<inf>2−x</inf> has been a critical point for fabricating efficient and stable perovskite solar cells (PSCs). Controlling oxygen vacancies in SnO<inf>2−x</inf> is an efficient strategy, but most research only presents the consequential results without scrutinizing the phenomenological part of the strategy. Here, we deeply examined and revealed a new beneficial effect of controlling oxygen vacancies in SnO<inf>2−x</inf>. Oxygen atoms of SnO<inf>2−x</inf> were responsible for retaining α-FAPbI<inf>3</inf> at the FAPbI<inf>3</inf>/SnO<inf>2−x</inf> interface by controlling the formation of iodine interstitials, which are strong initiators of unfavorable perovskite phase transitions. Using crystallographic analysis, we observed suppression of these phase transitions when oxygen vacancies were mitigated in SnO<inf>2−x</inf> by oxidized black phosphorus quantum dots. Furthermore, formamidinium (FA) cation retention was also observed as a beneficial effect of the strategy by introducing hydrogen bonding sources for FA cations at the interface. Our findings suggest the genuine necessity of oxygen vacancy reduction in SnO<inf>2−x</inf>. © 2022 Elsevier Inc.

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